Moisture protection for sleepers over slab on grade
My location is zip code 13420.
My foundation is a monolithic slab on grade. I installed a 16″ gravel base with Vapor Block 15 above and 2″ xps on top of the Vapor Block. The perimeter of the slab is also insulated with 2″ xps. Before I closed the project in the slab would get soaked with condensation when outside temperatures and humidity rose to the extent that it looked like it was hosed down. Closing in greatly reduced that effect, but my roof isn’t yet closed off from the interior – no drop ceiling at 2nd floor yet and gables and rafter ends are wide open – and the space isn’t heated, so after prolonged high humidity the floor can eventually get damp. A portion of the slab will get sleepers and hardwood flooring and I’m wondering what the best approach would be for minimizing moisture against the bottom of the sleepers. Felt, or thin rolled foam, or even 1/2″ xps. My thoughts are that once the space is completely closed in, insulated and conditioned that I’ll get no condensation on the concrete, but I’m wondering, given the gravel, Vapor Block, and foam, do I need to be all that concerned about protecting the sleepers or will what little moisture may migrate into the concrete be negligible? Thanks, Daniel
GBA Detail Library
A collection of one thousand construction details organized by climate and house part